1. Technical Field
The present invention relates to a dental blank to be machined, a metal powder for powder metallurgy, a dental metal frame for porcelain bonding, and a dental prosthesis.
2. Related Art
In the prosthesis of a missing part of a tooth crown or a missing tooth in a dental treatment, a crown, a bridge, or a denture is used in many cases. Among these, from the viewpoint of aesthetic appearance and functionality, a dental prosthesis obtained by bonding a ceramic material called “porcelain” to the surface of a metal frame is used.
JP-A-11-1738 discloses an alloy for a noble metal-based metal frame obtained by adding a metal element such as Sn, Ga, or In to a metal element such as Au, Pd, Cu, Ir, or Ag. This alloy can be molded into a desired shape by casting, and therefore, by bonding porcelain for tooth crown restoration to the surface of a metal frame formed from this alloy, a dental prosthesis having excellent aesthetic appearance can be obtained.
On the other hand, recently, a method for forming a metal frame based on shape data obtained by measuring the three-dimensional shape of an affected part is getting popularized. Such a mechanism is called “dental CAD/CAM system”. The CAD (computer aided design) is a system that acquires the three-dimensional shape data of an affected part with a 3D scanner or the like and digitizes the data. Further, the CAM (computer aided manufacturing) is a system that cuts out a metal frame having a shape suited to the affected part by machining a workpiece based on the digitized data generated by the CAD. The dental CAD/CAM system combining these systems can easily achieve high dimensional accuracy which had to rely on the skill of dental technicians in the past, and therefore is expected to be further popularized because it can efficiently form a metal frame that is in excellent conformity with the affected part (see, for example, JP-A-2007-215854).
The workpiece to be subjected to the dental CAD/CAM system is generally called “blank”. The blank is required to have machinability as well as properties necessary for a metal frame such as aesthetic appearance, biocompatibility, chemical stability, and abrasion resistance. The machinability is a property for enabling a favorable machining process, and by using a blank having favorable machinability, a metal frame having a desired shape accurately reproduced based on the digitized data generated by the CAD can be efficiently cut out by the CAM.
The alloy disclosed in JP-A-11-1738 is an alloy suited to the casting, but it has a problem in that the machinability is poor. If the machinability of a blank is low, the intended processing cannot be performed so that the shape after processing is deviated from the intended shape. As a result, it takes time and effort to perform a secondary process for correcting the shape and, because the conformity with an affected part is low, patients may feel discomfort.